You can turn on/off the wireless transmit of your router by pressing this button. Ofcourse before that you have to enable the service for that.
Therefore go to Services -> Services and tick Enable at the "SES / AOSS / EZ-SETUP Button" group

You can also run a script when the SES/AOSS/EZ-SETUP button is pressed, therefore have a look at Script types. **Note:** You must have "Use this button for turning off radio" disabled (see section immediately above)